Self-expanding neurostimulation leads having broad multi-electrode arrays

ABSTRACT

Self-expanding lead including a lead body having a distal body end, a proximal body end, and a central axis extending therebetween. The lead body includes first and second outer arms and an inner arm disposed between the first and second outer arms. The first and second outer arms and the inner arm extend lengthwise between the proximal body end and the distal body end. The lead also includes an array of electrodes that are configured to apply a neurostimulation therapy within an epidural space of a patient. At least some of the electrodes are positioned along the first and second outer arms. Each of the first and second outer arms includes a resilient member that is biased to flex the corresponding first and second outer arms from a collapsed condition to an expanded condition in a lateral direction away from the inner arm.

RELATED APPLICATION

The present application claims the benefit of U.S. ProvisionalApplication No. 61/753,429, filed on 16 Jan. 2013, which is incorporatedby reference in its entirety.

FIELD OF THE INVENTION

One or more embodiments of the subject matter described herein generallyrelate to systems having leads for generating electric fields proximateto nerve tissue.

BACKGROUND

Neurostimulation systems (NS) include devices that generate electricalpulses and deliver the pulses to nerve tissue to treat a variety ofdisorders. Spinal cord stimulation (SCS) is a common type ofneurostimulation. In SCS, electrical pulses are delivered to nervetissue in the spine typically for the purpose of chronic pain control.While a precise understanding of the interaction between the appliedelectrical energy and the nerve tissue is not fully appreciated, it isknown that application of an electric field to spinal nerve tissue caneffectively mask or alleviate certain types of pain transmitted fromregions of the body associated with the stimulated nerve tissue. SCS mayhave applications other than pain alleviation as well.

NS and SCS systems generally include a pulse generator and one or moreleads electrically coupled to the pulse generator. A lead includes anelongated body of insulative material. A stimulating end portion of thelead includes multiple electrodes that are electrically coupled to thepulse generator through wire conductors. The stimulating end portion ofa lead is implanted proximate to nerve tissue (e.g., within epiduralspace of a spinal cord) to deliver the electrical pulses. A trailing endportion of the lead body includes multiple terminal contacts, which arealso electrically coupled to the wire conductors. The terminal contacts,in turn, are electrically coupled to the pulse generator. The terminalcontacts receive electrical pulses from the pulse generator that arethen delivered to the electrodes through the wire conductors to generatethe electric fields. The pulse generator is typically implanted withinthe individual and may be programmed (and re-programmed) to provide theelectrical pulses in accordance with a designated sequence.

Typically, one of two types of leads is used. The first type is apercutaneous lead, which has a rod-like shape and includes electrodesspaced apart from each other along a single axis. The second type oflead is a laminectomy or laminotomy lead (hereinafter referred to as apaddle lead). A paddle lead has an elongated planar body with a thinrectangular shape (i.e., paddle-like shape). Although the paddle leadmay include only one row or column of electrodes, the paddle leadtypically includes an array of electrodes that are spaced apart fromeach other along a substantially common plane. The number of electrodesmay be, for example, two, four, eight, or sixteen.

A single paddle lead enables more coverage of the nerve tissue relativeto a single percutaneous lead. However, due to their dimensions andphysical characteristics, paddle leads require a surgical procedure(e.g. a partial laminectomy) to implant the lead. The paddle lead istypically positioned within the epidural space adjacent to the dura ofthe spinal cord. Conventional percutaneous leads are inserted into thebody through a narrow introducer. Compared to paddle leads, thepercutaneous leads have dimensions that may enable an easier insertioninto the spinal cord and/or may cause less trauma to the insertion siteof the spinal cord.

Therefore, a need remains for implantable leads that may be insertedinto the spinal cord with a simpler insertion procedure thanconventional paddle leads and also have electrode coverage of the nervetissue that is broader than conventional percutaneous leads.

BRIEF SUMMARY

In accordance with an embodiment, a self-expanding lead is provided thatincludes a lead body having a distal body end, a proximal body end, anda central axis extending therebetween. The lead body includes first andsecond outer arms and an inner arm disposed between the first and secondouter arms. The first and second outer arms and the inner arm extendlengthwise between the proximal body end and the distal body end. Thelead also includes an array of electrodes that are configured to apply aneurostimulation therapy within an epidural space of a patient. At leastsome of the electrodes are positioned along the first and second outerarms. Each of the first and second outer arms includes a resilientmember that is biased to flex the respective outer arm from a collapsedcondition to an expanded condition in a direction that is away from theinner arm. The resilient member permits the respective outer arm to flextoward the inner arm from the expanded condition to the collapsedcondition when a force is applied.

In accordance with another embodiment, a self-expanding lead is providedthat includes first and second outer arms extending between respectiveproximal and distal arm ends. Each of the first and second outer armsincludes electrodes that are positioned along a length of the respectiveouter arm. The lead also includes an inner arm that is disposed betweenthe first and second outer arms. The inner arm extends between arespective base end and a respective distal arm end. The proximal endsof the inner arm and the first and second outer arms are coupled to eachother proximate to a proximal body end of the self-expanding lead. Thelead also includes a multi-electrode array having the electrodes of thefirst and second arms. The multi-electrode array is configured to applya neurostimulation therapy within an epidural space of a patient. Eachof the first and second outer arms includes a resilient member that isbiased to flex the respective outer arm from a collapsed condition to anexpanded condition in a direction that is away from the inner arm. Theresilient member permits the respective outer arm to flex toward theinner arm from the expanded condition to the collapsed condition when aforce is applied.

While multiple embodiments are described, still other embodiments of thedescribed subject matter will become apparent to those skilled in theart from the following detailed description and drawings, which show anddescribe illustrative embodiments of disclosed inventive subject matter.As will be realized, the inventive subject matter is capable ofmodifications in various aspects, all without departing from the spiritand scope of the described subject matter. Accordingly, the drawings anddetailed description are to be regarded as illustrative in nature andnot restrictive.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view of one embodiment of a neurostimulating (NS)system in accordance with one embodiment.

FIG. 2A illustrates a plan view of a self-expanding lead that is in anexpanded or relaxed state in accordance with one embodiment.

FIG. 2B is an enlarged view of a distal portion of the self-expandinglead shown in FIG. 2A.

FIG. 2C is an enlarged view of a proximal portion of the self-expandinglead shown in FIG. 2A.

FIG. 3 is a cross-section of the self-expanding lead taken along theline 3-3 in FIG. 2A while in the expanded state.

FIG. 4 is a cross-section of the self-expanding lead taken along theline 4-4 in FIG. 2A while in the expanded state.

FIG. 5 is a cross-section of the self-expanding lead taken along theline 5-5 in FIG. 2A while in the expanded state.

FIG. 6 is a cross-section of the self-expanding lead in a collapsedstate while within an insertion tool in accordance with one embodiment.

FIG. 7 is a cross-section of a self-expanding lead in accordance withone embodiment while the lead is in a collapsed state within aninsertion tool.

FIG. 8 illustrates a series of stages during an insertion process inwhich a self-expanding lead clears an insertion tool.

FIG. 9 illustrates a guide wire device that may be used to direct aself-expanding lead into an anatomical space of a patient in accordancewith one embodiment.

FIG. 10 is a perspective view of a self-expanding lead in accordancewith one embodiment that utilizes a flexible membrane.

FIG. 11 is a cross-section of a self-expanding lead having a flexiblemembrane in accordance with one embodiment.

FIG. 12 is a cross-section of a self-expanding lead having a flexiblemembrane in accordance with one embodiment.

FIG. 13 illustrates a plan view of a self-expanding lead that is in anexpanded state in accordance with one embodiment.

FIG. 14 illustrates a plan view of a self-expanding lead that is in anexpanded state in accordance with one embodiment.

FIG. 15 is a block diagram illustrating a method of manufacturing aself-expandable lead in accordance with one embodiment.

DETAILED DESCRIPTION

Embodiments described herein include self-expanding leads that arecapable of flexing into an operative shape or configuration as theself-expanding lead is inserted into the epidural space. For example,the self-expanding lead may include one or more resilient members thatare biased to expand the self-expanding lead when the self-expandinglead is permitted to expand (e.g., when a force is removed). Theself-expanding lead may include a plurality of arms, at least one ofwhich may be capable of flexing into an expanded condition. Theindividual arms may reduce the amount of pressure along the spinalnerves within the epidural space relative to conventional paddle leads.

The individual arms of the lead may include one or more electrodes.Collectively, the electrodes of the individual arms may form amulti-electrode array (e.g., two-dimensional array) that provideselectrode coverage comparable to conventional paddle leads. Forinstance, the multi-electrode array may be configured to have a coveragesimilar to Penta™ paddle leads distributed by St. Jude. In addition tothe broad electrode coverage, the expandable/collapsible lead may enabledelivery of the lead through introducers that are typically used forinserting percutaneous leads. As such, incisions for inserting the leadinto the patient may be smaller than those used for inserting paddleleads, which may reduce recovery and clinical cost.

FIG. 1 depicts a neurostimulation (NS) system 100 that generateselectrical pulses for application to tissue, such as spinal cord tissue,of a patient according to one embodiment. For embodiments that stimulatespinal cord tissue, the nerve tissue may include dorsal column (DC)fibers and/or dorsal root (DR) fibers. The NS system 100 includes an NSdevice (or pulse generator) 150 that is adapted to generate electricalpulses in order to apply electric fields to the tissue. The NS device150 is typically implantable within an individual (e.g., patient) and,as such, may be referred to as an implantable pulse generator (IPG). Theimplantable NS device 150 typically comprises a housing 158 thatencloses a controller 151, which may include or be operably coupled to apulse generating circuit module 152, a charging coil 153, a battery 154,a far-field and/or near field communication circuit module 155, abattery charging circuit module 156, a switching circuit module 157,etc. of the device. The controller 151 may include a processor or otherlogic-based device for controlling the various other components of theNS device 150. Software code is typically stored in memory of the NSdevice 150 for execution by the NS device 150 to control the variouscomponents of the device.

The controller 151 may be programmable controller that controls thevarious modes of stimulation therapy for the NS device 150. Thecontroller 151 may include a microprocessor, or equivalent controlcircuitry, designed specifically for controlling delivery of stimulationtherapy and may further include RAM or ROM memory, logic and timingcircuitry, state machine circuitry, and I/O circuitry. Themicrocontroller 151 may have the ability to process or monitor inputsignals (data) as controlled by a program code stored in memory. Thedetails of the design and operation of the microcontroller 151 are notcritical to the present invention. Rather, any suitable microcontroller151 may be used.

FIG. 1 illustrates various blocks in which some of the blocks arereferred to as a “circuit module.” It is to be understood that thecircuit modules that may be implemented as hardware with associatedinstructions (e.g., software stored on a tangible and non-transitorycomputer readable storage medium, such as a computer hard drive, ROM,RAM, or the like) that perform the operations described herein. Thehardware may include state machine circuitry hard wired to perform thefunctions described herein. Optionally, the hardware may includeelectronic circuits that include and/or are connected to one or morelogic-based devices, such as microprocessors, processors, controllers,or the like. Optionally, the circuit modules may represent processingcircuitry such as one or more field programmable gate array (FPGA),application specific integrated circuit (ASIC), or microprocessor. Thecircuit modules in various embodiments may be configured to execute oneor more algorithms to perform functions described herein. The one ormore algorithms may include aspects of embodiments disclosed herein,whether or not expressly identified in a flowchart or a method.

The NS device 150 may comprise a separate or an attached extensioncomponent 170. If the extension component 170 is a separate component,the extension component 170 may connect with the “header” portion of theNS device 150 as is known in the art. If the extension component 170 isintegrated with the NS device 150, internal electrical connections maybe made through respective conductive components. Within the NS device150, electrical pulses are generated by the pulse generating circuitmodule 152 and are provided to the switching circuit module 157. Theswitching circuit module 157 connects to outputs of the NS device 150.Electrical connectors (e.g., “Bal-Seal” connectors) within a connectorportion 171 of the extension component 170 or within the header portionmay be employed to conduct the electrical pulses. Terminal contacts (notshown) of one or more neurostimulator leads 110 are inserted within theconnector portion 171 or within the header for electrical connectionwith respective connectors. Thereby, the pulses originating from NSdevice 150 are provided to the neurostimulator lead 110. The pulses arethen conducted through wire conductors of the lead 110 and applied totissue of an individual via electrodes 111. In the illustratedembodiment, the neurostimulator lead is a lead configured for insertionafter a laminectomy or a laminotomy. The neurostimulator lead 110 ishereinafter referred to as a “self-expanding lead.”

For implementation of the components within NS device 150, a processorand associated charge control circuitry for an implantable pulsegenerator is described in U.S. Patent Application Publication No.2006/0259098, entitled “SYSTEMS AND METHODS FOR USE IN PULSEGENERATION,” which is incorporated herein by reference in its entirety.Circuitry for recharging a rechargeable battery of an implantable pulsegenerator using inductive coupling and external charging circuits aredescribed in U.S. Pat. No. 7,212,110, entitled “IMPLANTABLE DEVICE ANDSYSTEM FOR WIRELESS COMMUNICATION,” which is incorporated herein byreference in its entirety. One or more NS devices and one or more paddleleads that may be used with embodiments described herein are describedin U.S. Patent Application Publication No. US 2013/0006341 in itsentirety.

An example and discussion of “constant current” pulse generatingcircuitry is provided in U.S. Patent Application Publication No.2006/0170486 entitled “PULSE GENERATOR HAVING AN EFFICIENT FRACTIONALVOLTAGE CONVERTER AND METHOD OF USE,” which is incorporated herein byreference in its entirety. One or multiple sets of such circuitry may beprovided within the NS device 150. Different pulses on differentelectrodes may be generated using a single set of pulse generatingcircuitry using consecutively generated pulses according to a“multi-stimset program.” Complex pulse parameters may be employed suchas those described in U.S. Pat. No. 7,228,179, entitled “METHOD ANDAPPARATUS FOR PROVIDING COMPLEX TISSUE STIMULATION PATTERNS,” andInternational Patent Publication No. WO 2001/093953 A1, entitled“NEUROMODULATION THERAPY SYSTEM,” each of which is incorporated hereinby reference in its entirety. Alternatively, multiple sets of suchcircuitry may be employed to provide pulse patterns that includesimultaneously generated and delivered stimulation pulses throughvarious electrodes of one or more stimulation leads as is also known inthe art. Various sets of parameters may define the pulse characteristicsand pulse timing for the pulses applied to various electrodes as isknown in the art. Although constant current pulse generating circuitryis contemplated for some embodiments, any other suitable type of pulsegenerating circuitry may be employed such as constant voltage pulsegenerating circuitry.

In some embodiments, a controller device 160 may be implemented torecharge battery 154 of the NS device 150. For example, a wand 165 maybe electrically connected to the controller device 160 through suitableelectrical connectors (not shown). The electrical connectors may beelectrically connected to a primary coil 166 at the distal end of wand165 through respective wires (not shown). The primary coil 166 may beplaced against the patient's body immediately above the charging coil(or secondary coil) 153 of the NS device 150. The controller device 160may generate an AC-signal to drive current through the primary coil 166.Current may be induced in the secondary coil 153 to recharge the battery154.

In some embodiments, the controller device 160 preferably provides oneor more user interfaces to allow the user to the NS device 150 accordingto one or more stimulation programs to treat the patient's disorder(s).Each stimulation program may include one or more sets of stimulationparameters including pulse amplitude, pulse width, pulse frequency orinter-pulse period, pulse repetition parameter (e.g., number of timesfor a given pulse to be repeated for respective stimset during executionof program), etc. The NS device 150 modifies its internal parameters inresponse to the control signals from controller device 160 to vary thestimulation characteristics of stimulation pulses transmitted throughstimulation lead 110 to the tissue of the patient. Neurostimulationsystems, stimsets, and multi-stimset programs are discussed in PCTPublication No. WO 01/93953, entitled “NEUROMODULATION THERAPY SYSTEM,”and U.S. Pat. No. 7,228,179, entitled “METHOD AND APPARATUS FORPROVIDING COMPLEX TISSUE STIMULATION PATTERNS,” which are incorporatedherein by reference.

FIG. 2A is a plan view of a self-expandable lead 200 and includes twoisolated, enlarged views of the lead 200. The lead 200 may be similar oridentical to the lead 110 (FIG. 1) and may be used with an NS system,such as the NS system 100 (FIG. 1). The lead 200 includes a lead body202 having a distal body end 204, a proximal body end 206, and a centralaxis 208 extending therebetween. A portion of the lead body 202 near thedistal body end 204 is shown in greater detail in FIG. 2B, and a portionof the lead body 202 near the proximal body end 206 is shown in greaterdetail in FIG. 2C. With respect to FIG. 2A, the central axis 208 extendsgenerally along a geometric center of a cross-section of the lead 200.As shown, the lead body 202 includes a plurality of arms or splines211-215 that extend lengthwise between the distal body end 204 and theproximal body end 206 of the lead body 202.

In the illustrated embodiment, the arms 211-215 include first and secondouter arms 211, 214, first and second inner arms 212, 213, and a centerinner arm 215. The inner arms 212, 213, 215 are disposed between theouter arms 211, 214, and the center inner arm 215 is disposed betweenthe first and second inner arms 212, 213. In some embodiments, the innerarms 212, 213 may be described or characterized intermediate arms 212,213. Each of the arms 211-215 extends lengthwise between a respectivedistal arm end 218 (shown in FIG. 2B) and a respective proximal arm end220 (shown in FIG. 2C). The distal arm ends 218 are located proximate tothe distal body end 204, and the proximal arm ends 220 are locatedproximate to the proximal body end 206. The proximal body end 206 mayinclude an end 216 (or cable end) of a lead cable 210. The lead body 202also includes a first paddle side 222, which is shown in FIG. 2, and asecond paddle side 224 (shown in FIG. 3). The first and second paddlesides 222, 224 face in opposite directions and extend lengthwise betweenthe distal body end 204 and the proximal body end 206.

In the illustrated embodiment, the lead body 202 has a lead profile orfootprint 225 that constitutes a spatial volume defined by exteriorsurfaces of the lead body 202 when the leady body 202 is in a relaxedstate. In FIG. 2, the lead profile 225 is represented by a dashed linethat extends alongside a perimeter of the lead body 202. Forillustrative purposes, the dashed line is spaced apart from the exteriorsurfaces of the lead body 202 that define the lead profile 225. By wayof example, the lead body 202 may have a first dimension or width 231that extends between exterior surfaces of the outer arms 211, 214 andwhich face in opposite directions. The lead body 202 also has a seconddimension or length 232 that extends between an exterior surface of thedistal body end 204 and a location where the proximal body end 206 joinsthe lead cable 210. The lead body 202 may also have a third dimension orthickness 233 (shown in FIG. 3) that extends between paddle sides 222,224. Each of the width 231, the length 232, and the thickness 233 mayhave a varying or non-uniform value as the lead body 202 extends alongthe dimensions. For instance, the length 232 is greatest when measuredalong the central axis 208.

As shown, the lead profile 225 may include elongated windows or openings241-244 that are defined between adjacent arms. More specifically, withrespect to the illustrated embodiment, the lead body 202 defines theelongated window 241 between the outer arm 211 and the inner arm 212,the elongated window 242 between the inner arm 212 and the inner arm215, the elongated window 243 between the inner arm 215 and the innerarm 213, and the elongated window 244 between the inner arm 213 and theouter arm 214. The elongated windows 241 extend lengthwise along thecentral axis 208 and widthwise between the adjacent arms. The elongatedwindows 241-244 reduce or shrink when the lead 200 is in a collapsedstate.

When the lead 200 is in a relaxed state prior to insertion as shown inFIG. 2, the lead profile 225 of the lead body 202 may be substantiallyplanar widthwise and lengthwise. For example, the arms 211-215 may besubstantially coplanar (e.g., substantially coincide along a commonplane). In other embodiments, the lead profile 225 may have a curvedcontour when the lead body 202 is in a relaxed state. For example, thelead profile 225 may curve as the lead body 202 extends along the length232 (e.g., such that the central axis 208 is not linear and has a curvedor bent shape) and/or as the lead body 202 extends along the width 231(e.g., the lead body 202 may be C-shaped as viewed along the centralaxis 208). The contours may be predetermined by the manufacturingprocess of the lead 200. For example, the contours may be predeterminedto complement the anatomical structure that the lead 200 will interface.

During an implantation procedure, the distal body end 204 is typicallythe first end that is inserted through an incision and into the spinalcolumn. As shown, the lead cable 210 extends away from the lead body 202from the proximal body end 206. The lead cable 210 may includeconductive pathways 286 (shown in FIG. 3), such as wire conductors,which extend from the lead body 202 to an NS device or pulse generator(not shown), such as the NS device 150 (FIG. 1). The conductive pathways286 also extend lengthwise along the arms 211-215 to electrically couplethe corresponding electrodes 250 to the pulse generator.

As shown in FIG. 2, the lead 200 also includes a plurality of electrodes250 that are disposed along the outer arms 211, 214 and the inner arms212, 213, but not the inner arm 215. In other embodiments, the inner arm215 may include one or more of the electrodes 250. The electrodes 250may comprise Platinum-Iridium (Pt—Ir) or other equivalent material. Asone specific example only, the electrodes may be 90-10 Pt—Ir (i.e., 90%Platinum, 10% Iridium). The electrodes 250 may be positioned relative toeach other to form a multi-electrode array 252. The multi-electrodearray 252 is a two-dimensional array in the illustrated embodiment. Theelectrodes 250 and/or the multi-electrode array 252 may be configured toprovide a neurostimulation therapy in an epidural space of a patient.For example, electrical pulses transmitted from the NS device 150 may beprovided at a predetermined schedule or frequency to provide therapy tothe patient. It is noted that the FIG. 2 illustrates only onearrangement of the electrodes 250. However, in other embodiments, theelectrodes 250 may have any one of a variety of arrangements.

When the lead 200 is disposed in the epidural space, one of the paddlesides may interface with nerve tissue and the other paddle side mayinterface with an anatomical structure (e.g., bone, ligament, or otherportions of the spine). In some embodiments, the electrodes 250 may beexposed along each of the paddle sides 222, 224. In other embodiments,the electrodes 250 may be exposed only along one of the paddle sides,such as the paddle side 222 shown in FIG. 2, and not the other paddleside.

In the illustrated embodiment, each of the outer arms 211, 214 and eachof the inner arms 212, 213 include a series or column of electrodes 250that are spaced apart from each other along a length of the respectivearm. When in an operative state (e.g., an expanded state), the arms arespaced apart from each other thereby laterally separating the electrodes250 of adjacent arms. To form the multi-electrode array 252 with apredetermined configuration, the electrodes 250 may be disposed alongthe lengths of the respective arms at designated locations and the arms211-215 may be configured to have a designated separation when in theexpanded state so that the electrodes 250 form the multi-electrode array252.

In the illustrated embodiment, multi-electrode array 252 includes a 4×5grid of electrodes 250 in which the electrodes 250 are substantiallyevenly distributed along (e.g. parallel to) the central axis 208. Inalternative embodiments, the electrodes 250 may form a single row orcolumn that extends along the central axis 208 and are spaced apart fromeach other. In other embodiments, the multi-electrode array 252 may havea 4×4 grid of electrodes 250 or a 4×8 grid of electrodes 250. Inparticular embodiments, the multi-electrode array 252 may be configuredto have a coverage similar to Penta™ paddle leads distributed by St.Jude.

To this end, the lead body 202 may include a plurality of resilientmembers 261-264 (shown in FIG. 2B) proximate to the distal body end 204and a plurality of resilient members 271-274 (shown in FIG. 2C)proximate to the proximal body end 206. In the illustrated embodiment,the resilient members 261-264 are located within the arms 211-214,respectively, and the resilient members 271-274 are located within thearms 211-214, respectively. In an exemplary embodiment, the resilientmembers 261-264 and 271-274 include a resilient material that is capableof being collapsed when a force is applied and biased to flex back to adesignated shape when the force is removed. In certain embodiments, theresilient material is a metal or metal alloy. The resilient material mayhave shape memory. In particular embodiments, the resilient materialincludes nitinol, which is a metal alloy of nickel and titanium.However, other materials, including combinations of materials, may beused.

FIGS. 2A-2C show the lead 200 in a relaxed or expanded state. Theresilient members are biased to flex the respective arm from a collapsedcondition to an expanded condition in a direction that is away from thecentral axis 208 (or the center inner arm 215). The resilient membersalso permit the respective arm to flex toward the central axis 208 (orthe center inner arm 215) from the expanded condition to the collapsedcondition when a force is applied.

FIGS. 3-5 illustrate different cross-sections of the lead 200 as shownin FIG. 2A. FIG. 3 is taken along the line 3-3 in FIG. 2A andillustrates cross-section of the arms 211-215 in greater detail. Forillustrative purposes, the lead profile 225 is shown. The lead body 202includes the paddle sides 222 and 224. Each of the arms 211-215 has across-section that includes an arm width 281 and an arm height 283. Insome embodiments, the arm height 283 may be substantially equal to thethickness 233 of the lead body 202 or the lead profile 225 at thecross-section shown in FIG. 3. In particular embodiments, the arms211-215 are narrow, elongated splines or beams in which the arm width281 and the arm height 283 are approximately equal. For example, the armwidth 281 and the arm height 283 may differ by at most 50% of thegreater of the arm width 281 and the arm height 283. For example, if thearm width 281 were about 1.5 mm, the arm height 283 may be about 0.75mm. If the arm height 283 is larger and is, for example, about 1.0 mm,the arm width 281 may be about 0.75 mm. In other embodiments, the armwidth 281 and the arm height 283 may differ by at most 25% of thegreater of the arm width 281 and the arm height 283 or, moreparticularly, by at most 10% of the greater of the arm width 281 and thearm height 283.

In the illustrated embodiment, the cross-section of the arms 211-215have a substantially circular shape or substantially square shape suchthat the arm width 281 and the arm height 283 are substantially equal Inother embodiments, the arms 211-215 may have a substantially rectangularshape. For example, the arm width 281 may be about 2.25 mm and the armheight 283 may be about 1.0 mm.

As shown, the arms 211-215 comprise an insulative material 284 that mayinclude the exterior surfaces of the arms 211-215. In FIG. 3, the arms211-214 also include conductive pathways 286 (e.g., wire conductors).The conductive pathways 286 comprise a conductive material, such ascopper, and are configured to transmit electrical signals (e.g.,current) to corresponding electrodes 250 (FIG. 2A). The conductivepathways 286 are electrically coupled to the pulse generator of the NSsystem 100. As described above, a designated frequency may betransmitted to the electrodes 250 in order to provide therapy to apatient. In an exemplary embodiment, the conductive pathways 286 mayinclude jackets that insulate the conductive pathways 286 from eachother.

The inner arm 215 includes a steering lumen 288. The steering lumen 288may be defined by an interior surface of the insulative material 284.The steering lumen 288 may extend lengthwise through the inner arm 215from the proximal body end 206 (FIGS. 2A and 2C) to and, optionally,through the distal body end 204 (FIGS. 2A and 2B). The steering lumen288 is sized and shaped to receive an elongated tool 290, such as aguide wire. The elongated tool 290 may be used during the insertionprocess to guide the lead 200 (FIG. 2A).

The insulative material 284 may include one or more biocompatiblematerials. Non-limiting examples of such materials include polyimide,polyetheretherketone (PEEK), polyethylene terephthalate (PET) film (alsoknown as polyester or Mylar), polytetrafluoroethylene (PTFE) (e.g.,Teflon), or parylene coating, polyether bloc amides, polyurethane. Insome embodiments, the material of the lead body 202 that surrounds themetal components (e.g., electrodes 250 and the conductive pathways 286that couple to the electrodes 250) includes at least one of polyimide,polyetheretherketone (PEEK), polyethylene terephthalate (PET) film,polytetrafluoroethylene (PTFE), parylene, polyether bloc amides, orpolyurethane.

FIG. 4 shows cross-sections of the arms 211-215 taken along the line 4-4of FIG. 2A. In FIG. 4, each of the arms 211-214 includes one of theelectrodes 250. The electrode 250 is configured to be exposed along anouter surface of the respective arm so that the electrode 250 mayinterface with an anatomical structure, such as nerve tissue. In FIG. 4,the electrodes 250 are completely exposed along the outer surface. Inother embodiments, one or more portions of the electrodes 250 may becovered such that the corresponding portion(s) is not exposed. Forinstance, the insulative material 284 may cover the one or more portionsof the electrodes 250. As shown in FIG. 4, the electrode 250 may beseparated from an adjacent electrode 250 by a gap 292. The gaps 292 maybe part of the elongated windows 241-244.

FIG. 5 shows cross-sections of the joints 265-268 of the respective arms211-215 (FIG. 2A) taken along the line 5-5 in FIG. 2A. As shown, each ofthe joints 265-268 includes the respective resilient member 261-264 thatis at least partially surrounded by the insulative material 284. Theresilient members 261-264 of the respective joints 265-268 aredimensioned and shaped to function as described herein. For example, theresilient members 261-264 may be etched, creased, and/or have varyingdimensions in order to provide sufficient resiliency for returning thearms 211-214 to the expanded state when the force is removed. In someembodiments, the resilient members 261-264 may be etched (e.g.,laser-cut) to provide the designated shape.

FIG. 6 shows a cross-section of the lead body 202 when each of the arms211-214 is in a collapsed condition within an insertion tool 296, whichmay also be referenced as an introducer. The resilient members 261-264,271-274 (FIGS. 2B and 2C, respectively) may be configured such that thearms 211-214 collapse in a designated manner. For example, the resilientmembers 261-264, 271-274 may be shaped such that when a laterally-inwardforce F₁ (indicated by the inwardly pointing arrows) is provided, thearms 211-214 collapse toward (e.g., move toward) the inner arm 215and/or the central axis 208. The laterally-inward force F₁ may beapplied when the lead body 202 is drawn into or advanced into a cavityof an insertion tool. The cavity may be defined by interior surfaces ofthe insertion tool. The lead body 202 may slide through the insertiontool when a linear force is applied. The linear force may be translatedinto the laterally-inward force F₁ as the unyielding interior surface ofthe insertion tool collapses the arms 211-214.

In the illustrated embodiment, when the lead body 202 is in an expandedstate, each of the arms 211-214 coincides with a body plane 298 prior tothe arms 211-214 collapsing. As the arms 211-214 collapse, the arms211-214 move along the body plane 298 in an inward direction toward theinner arm 215 and/or toward the central axis 208. When the arms 211-214are in the collapsed conditions as shown in FIG. 6, the arms 211-214 maybe co-planar with one another such that the arms 211-214 coincide withthe body plane 298.

FIG. 7 shows a cross-section of a lead body 302 when the lead body 302is located within an insertion tool 396. The lead body 302 may besimilar or identical to the lead body 202 (FIG. 2A). For example, thelead body 302 includes arms 311-315. As shown in FIG. 7, each of thearms 311-314 is in a collapsed condition within a cavity 397 of theinsertion tool 396. The cavity 397 is defined by one or more interiorsurfaces of the insertion tool 396. Although not shown, the arms 311-314may include resilient members, such as the resilient members 261-264,271-274 (FIGS. 2B and 2C, respectively), which may be configured toexpand the arms 311-314 in a designated manner and permit the arms311-314 to collapse in a designated manner. For instance, the resilientmembers may be shaped such that when an inward force F₂ (indicated byarrows) is provided, the arms 311-314 collapse toward the inner arm 315and/or a central axis 308 of the lead body 302. However, the resilientmembers of the arms 311-314 may be biased such that the arms 311-314move toward the inner arm 315 or the central axis 308 in a differentmanner than the arms 211-214 shown in FIG. 6. For instance, the innerarms 312, 313 may move above or below the inner arm 315 and the innerarms 311, 314 may move below or above the inner arms 312, 313,respectively. As such, the inner arms 311-315 may have a substantiallystacked or overlapping configuration as shown in FIG. 7. In otherembodiments, the stacked configuration may include the inner arms311-314 forming a square perimeter that surrounds the inner arm 315within a center of the stacked configuration.

FIG. 8 illustrates a series of stages 401-406 during an insertionprocess in which a self-expanding lead 410 clears an end opening 412 ofan insertion tool 414 (e.g., an introducer). The lead 410 may be similaror identical to other self-expanding leads described herein and have adistal body end 416 and a proximal body end 418 (shown with respect tothe stage 406). The lead 410 may include arms 421-424 that haveresilient members (not shown) that enable the arms 421-424 to flexbetween collapsed and expanded conditions. Unlike other self-expandableleads described herein, the lead 410 does not include a central innerarm through which a steering lumen extends. In alternative embodiments,the lead 410 may include such an inner arm.

At stage 401, the lead 410 is disposed within a cavity, such as thecavity 397 (FIG. 7), of the insertion tool 414. As described above, therelaxed state of the lead 410 may be the expanded state. When the lead410 is advanced into the cavity 397, interior surfaces of the insertiontool 414 that define the cavity may engage one or more of the arms, suchas the arms 421 and 424. The insertion tool 414 may resist lateraldeformation such that the insertion tool 414 pushes the arms 421 and 424and, consequently, the arms 422, 423 laterally-inward as the lead 410 isadvanced into the cavity. Thus, the linear insertion force that isapplied to the lead 410 may be translated by the interior surface(s) ofthe insertion tool 414 into a laterally-inward force that collapses thearms 211-214.

Before or after the lead 410 has been disposed within the insertion tool414, the insertion tool 414 may be advanced into a patient (not shown)through one or more incisions. For example, the insertion tool 414 maybe advanced through one or more incisions that provide access to thespinal cord (not shown). In some embodiments, the insertion tool 414 maybe identical to the introducers that are used to insert percutaneousleads into the spinal cord. In other embodiments, the insertion tool 414may not be identical, but may have dimensions that are approximate to orsimilar to the dimensions of conventional percutaneous introducers.

At stage 402, the distal body end 416 clears the end opening 412 of theinsertion tool 414. As the lead 410 transitions to stage 403, the distalbody end 416 may expand to have a larger lead profile. At this time, thedistal body end 416 may engage tissue within the anatomical space (notshown). Geometries of the anatomical space, including the epiduralspace, vary from patient to patient. In some cases, it may be desirablefor the lead 410 to be capable of moving around obstructions, such asbone or tissue, and/or to be capable for moving tissue without causingsignificant trauma to the patient. In accordance with some embodiments,the resiliency of the arms 421-424 at the distal body end 416 may beconfigured such that the distal body end 416 is capable of engaging andflexing to slide around tissue and/or is capable of engaging and movingtissue within the anatomical space.

At stage 404, the distal body end 416 has cleared the end opening 412 ofthe insertion tool 414 and a majority of a length of the lead 410 hasadvanced into the anatomical space. At stages 405 and 406, the proximalbody end 418 has expanded such that the arms 421-424 are fully expandedand the lead 410 has a maximum lead profile. Before or after the lead410 is properly position within the epidural space, the tool 414 may bewithdrawn through the one or more incision cites.

FIG. 9 illustrates a guiding device 500 that may be used to direct theself-expanding lead 200 into an anatomical space of a patient. As shown,the guiding device 500 includes a guide wire 502 that is operablycoupled to a handle 504 that is configured to be gripped by anindividual (e.g., doctor). In FIG. 9, the guide wire 502 is insertedentirely through the steering lumen 288 (FIG. 3) of the inner arm 215such that the guide wire 502 extends beyond the distal body end 204 ofthe lead 200.

The insertion process with respect to the lead 200 may be similar to theinsertion process described with respect to FIG. 8. However, before orafter the lead 200 is loaded into the insertion tool (not shown), theguide wire 502 of the guiding device 500 may be inserted through thesteering lumen 288 of the inner arm 215. After the insertion tool hasbeen advanced through the incision site and positioned proximate to thedesignated anatomical space as described above, the guide wire 502 maybe moved into the anatomical space before the lead 200 clears the endopening (not shown) of the insertion tool. With the guide wire 502located within the anatomical space, the lead 200 may be advanced intothe anatomical space with the guide wire 502 directing or guiding thelead 200. As the lead 200 is advanced into the anatomical space, thedistal body end 204 of the lead 200 expands. In some embodiments, theexpanding of the lead 200 may displace tissue or other obstructionsthereby permitting the guide wire 502 to advance. After the lead 200 haspartially expanded, the lead 200 may then be further advanced into theanatomical space.

FIGS. 10-13 illustrate self-expandable leads having flexible membranes.For some applications, it may be desirable to have a flexible membraneextend across the width of the lead and join the arms of the lead body.The flexible membranes may impede growth of tissue around the arms whichmay enable a simpler process for withdrawing the lead with a decreasedlikelihood of trauma or injury to the patient. For example, FIG. 10 is aperspective view of a self-expanding lead 600 that utilizes a flexiblemembrane 602 in accordance with one embodiment. Other than the flexiblemembrane 602, the lead 600 may be identical to the lead 200 (FIG. 2A).For example, the lead 200 may include a lead body 604 having arms611-615. In the, expanded state shown in FIG. 10, the lead body 604 hasfirst and second paddle sides 622, 624. Also shown, the lead 600includes elongated windows or openings 641-644 that are defined betweenadjacent arms. The flexible membrane 602 extends along the paddles side624 and covers the elongated windows 641-644.

FIG. 11 is a cross-section of the lead 600 taken along the line 11-11 inFIG. 10. The flexible membrane 602 may be attached to the arms 611-615along the paddle side 624 in one or more manners. For example, theflexible membrane 602 may comprise a biocompatible material, which maybe the same as or similar to the insulative material 284, that isattached by selectively applying heat to the flexible membrane 602. Inother embodiments, an adhesive may be applied to the flexible membrane602, which may then be attached to the arms 611-614.

In the embodiment of FIG. 11, the lead 600 has a uni-directionalconfiguration. More specifically, the flexible membrane 602 may extendalong the paddle side 624 such that electrodes 650 (FIG. 10) of the lead600 are covered by the flexible membrane 602 and are only exposed alongthe paddle side 622. In such embodiments, it may be necessary to orientthe lead 600 so that a predetermined paddle side interfaces with thenerve tissue.

FIG. 12 is a cross-section of a self-expanding lead 700 having aflexible membrane 702 in accordance with one embodiment. Other than theflexible membrane 702, the lead 700 may be identical to the lead 200(FIG. 2A). In the embodiment of FIG. 12, the flexible membrane 702 isapplied to a paddle side 724 of the lead 700. The flexible membrane 702may have electrode openings 752 that expose the electrodes 750 along thepaddle side 724. The electrode openings 752 may be fabricate by etchingthe flexible membrane 702 material after the flexible membrane 702 hasbeen applied to the paddle side 724. In some embodiments, the flexiblemembrane 702 may be applied through an injection molding process. Withinjection molding, the lead 700 may be positioned within a mold thatcovers portions of the electrodes 750 so that molten membrane materialcures at designated portions thereby forming the electrode openings 752.

Accordingly, embodiments described herein may have a flexible membranealong one or both paddle sides. The flexible membrane may limit adhesionof the self-expanding lead to the patient by limiting growth of tissueor other material within the epidural space around the arms of the lead.In such embodiments that utilize a flexible membrane, the flexiblemembrane may be capable of folding over within the cavity of theinsertion tool, such as the insertion tool 414, thereby permitting theexpanding/collapsing abilities of the leads described herein.

FIG. 13 illustrates a plan view of a self-expanding lead 850 in anexpanded state. The lead 850 may be similar to other leads describedherein, such as the lead 200 (FIG. 2A). For example, the lead 850includes a lead body 852 having a distal body end 854, a proximal bodyend 856, and a central axis 858 extending therebetween. The proximalbody end 856 may include an end 866 (or cable end) of a lead cable 860.As shown, the lead body 852 includes a plurality of arms or splines861-865 that extend lengthwise between the distal body end 854 and theproximal body end 856 along the central axis 858. In the illustratedembodiment, the arms 861-865 include first and second outer arms 861,864, first and second inner arms 862, 863, and a center inner arm 865.The inner arms 862, 863, 865 are disposed between the outer arms 861,864, and the center inner arm 865 is disposed between the first andsecond inner arms 862, 863.

The lead cable 860 may include conductive pathways (not shown), such aswire conductors, which extend from the lead body 852 to an NS device orpulse generator (not shown), such as the NS device 150 (FIG. 1). Theconductive pathways also extend lengthwise along the arms 861-865 toelectrically couple corresponding electrodes 890 to the pulse generator.As shown, the corresponding electrodes 890 are disposed along each ofthe arms 861-865, including the inner arm 865. The electrodes 890 may bepositioned relative to each other to form a multi-electrode array 896.

Although not shown, the lead body 852 may include a plurality ofresilient members proximate to the distal body end 854 and a pluralityof resilient members proximate to the proximal body end 856. Theresilient members may be similar to the resilient members 261-264 and271-274 (FIGS. 2B and 2C, respectively) described with respect to thelead 200 and located within the arms. The resilient members may includea resilient material that is capable of being collapsed when a force isapplied and biased to flex back to a designated shape when the force isremoved.

In the illustrated embodiment, the inner arm 865 includes a steeringlumen 888. The steering lumen 888 extends through the lead cable 860into the inner arm 865. The steering lumen 888 may be defined by aninterior surface of an insulative material of the lead cable 860 and theinner arm 865. As shown, the steering lumen 888 extends lengthwisethrough the inner arm 865 from the proximal body end 856 and through thedistal body end 854. The steering lumen 888 is sized and shaped toreceive an elongated tool, which is illustrated as a guide wire 892 inFIG. 13. The guide wire 892 may be used during the insertion process toguide the lead 850 to a designated position in the epidural space (notshown). More specifically, the distal body end 854 may have an openingthat permits a wire end 894 of the guide wire 892 to clear the distalbody end 854 and be positioned within the epidural. With the wire end894 located within the epidural space, the lead 850 may then be directedalong the guide wire 892 and delivered to the epidural space. The pathtaken by the lead 850 is determined by the shape of the guide wire 892.

In some embodiments, the center inner arm 865 may not include resilientmaterial for flexing between different positions. For example, inparticular embodiments, the center inner arm 865 may not include suchresilient material and, instead, may include a more rigid material. Therigid material may be more suitable for receiving a tool, such as theguide wire 892.

FIG. 14 illustrates a plan view of a self-expanding lead 900 in anexpanded state. The lead 900 may have a lead body 902 that is similar inshape as the lead body 852. However, as shown in FIG. 14, a center innerarm 925 of the lead body 902 may not have a steering lumen that extendsentirely through the lead body 902. Instead, the center inner arm 925may end short of a distal body end 932 and permit inner arms 922 and 923to be directly coupled by a joint 927 and outer arms 921 and 924 to bedirectly coupled by a joint 928.

However, the lead body 902 may have a steering lumen 904 that extends toand ends at a cable end 906 of a lead cable 908. As shown, a guide wire910 may be inserted into the steering lumen 904 until a wire end 912 ofthe guide wire 910 engages the cable end 906 of the lead body 902. Theguide wire 910 may be operated to move the lead body 902 into adesignated orientation. For example, when the lead body 902 is insertedinto the epidural space (not shown), the lead body 902 may be moved tointo a designated orientation by the guide wire 910. More specifically,the lead body 902 may pivot (as indicated by the arrows) about a point930 located within the cable end 906.

FIG. 15 is a block diagram illustrating a method 800 of manufacturing aself-expandable lead in accordance with one embodiment. The lead may besimilar to the leads shown and described in the present application. Themethod 800 includes fabricating (at 802) resilient members. Theresilient members may be fabricated (at 802) by etching a sheet ofresilient material (e.g., metal alloy or plastic). In particularembodiments, the sheet of resilient material includes nitinol. Theetching may include laser-cutting the sheet material. The resilientmembers may be elongated structures that extend along curved paths. Forinstance, in a relaxed state, the resilient members may extend alongcurved paths that have similar shapes as the arms that the resilientmembers will be located within. As one example, the resilient membersmay be shaped similar to the resilient members 261-264 and 271-274 shownin FIGS. 2B and 2C, respectively.

The method 800 also includes assembling (at 804) wire conductors andelectrodes of the lead. The assembling (at 804) may include positioningthe resilient members relative to the wire conductors and theelectrodes. At 806, an insulative material may be applied (e.g., molded)to the assembly of wire conductors, electrodes, and resilient members.The insulative material may be a biocompatible material, such as thematerials described herein. The insulative material may completely coveror insulate the wire conductors and at least partially cover theelectrodes. The resilient members may be at least partially covered bythe insulative material.

A lead body may be formed upon applying the insulative material at 806.The lead body may be similar to other leads or lead bodies describedherein, such as the lead body 200. In particular, the lead body mayinclude a plurality of arms that extend between a distal body end and aproximal body end of the lead body. For example, the arms may includefirst and second outer arms and an inner arm generally disposed betweenthe first and second outer arms. The first and second outer arms and theinner arm may extend lengthwise between the proximal body end and thedistal body end.

The electrodes may form a multi-electrode array that is configured toapply a neurostimulation therapy. Some or all of the electrodes may bepositioned along the first and second outer arms. Each of the first andsecond outer arms may include at least one of the resilient members. Theresilient members may bias the respective outer arm to flex from acollapsed condition to an expanded condition in a laterally-outwarddirection. The resilient members may also permit the respective outerarm to flex laterally-inward from the expanded condition to thecollapsed condition when a force is applied.

Optionally, at 808, a flexible membrane may be applied to a paddle sideof the lead body. The flexible membrane may be similar to the flexiblemembranes 602 or 702 (FIGS. 10 and 12, respectively). In someembodiments, the flexible membrane may be applied (at 808) after thelead body is formed. In other embodiments, the flexible membrane may beapplied as the lead body is formed. For example, the flexible membranemay be molded with the arms of the lead body. In some embodiments, aflexible membrane may be applied on each of the paddle sides.

It is to be understood that the subject matter described herein is notlimited in its application to the details of construction and thearrangement of components set forth in the description herein orillustrated in the drawings hereof. The subject matter described hereinis capable of other embodiments and of being practiced or of beingcarried out in various ways. Also, it is to be understood that thephraseology and terminology used herein is for the purpose ofdescription and should not be regarded as limiting. The use of“including,” “comprising,” or “having” and variations thereof herein ismeant to encompass the items listed thereafter and equivalents thereofas well as additional items.

Unless specified or limited otherwise, the terms “mounted,” “connected,”“supported,” and “coupled” and variations thereof are used broadly andencompass both direct and indirect mountings, connections, supports, andcouplings. Further, “connected” and “coupled” are not restricted tophysical or mechanical connections or couplings. Also, it is to beunderstood that phraseology and terminology used herein with referenceto device or element orientation (such as, for example, terms like“central,” “upper,” “lower,” “front,” “rear,” “distal,” “proximal,” andthe like) are only used to simplify description of one or moreembodiments described herein, and do not alone indicate or imply thatthe device or element referred to must have a particular orientation. Inaddition, terms such as “outer” and “inner” are used herein for purposesof description and are not intended to indicate or imply relativeimportance or significance.

It is to be understood that the above description is intended to beillustrative, and not restrictive. For example, the above-describedembodiments (and/or aspects thereof) may be used in combination witheach other. In addition, many modifications may be made to adapt aparticular situation or material to the teachings of the presentlydescribed subject matter without departing from its scope. While thedimensions, types of materials and coatings described herein areintended to define the parameters of the disclosed subject matter, theyare by no means limiting and are exemplary embodiments. Many otherembodiments will be apparent to those of skill in the art upon reviewingthe above description. The scope of the inventive subject matter should,therefore, be determined with reference to the appended claims, alongwith the full scope of equivalents to which such claims are entitled. Inthe appended claims, the terms “including” and “in which” are used asthe plain-English equivalents of the respective terms “comprising” and“wherein.” Moreover, in the following claims, the terms “first,”“second,” and “third,” etc. are used merely as labels, and are notintended to impose numerical requirements on their objects. Further, thelimitations of the following claims are not written inmeans—plus-function format and are not intended to be interpreted basedon 35 U.S.C. §112, sixth paragraph, unless and until such claimlimitations expressly use the phrase “means for” followed by a statementof function void of further structure.

The following claims recite aspects of certain embodiments of theinventive subject matter and are considered to be part of the abovedisclosure.

What is claimed is:
 1. A self-expanding lead comprising: a lead bodyhaving a distal body end, a proximal body end, and a central axisextending therebetween, the lead body comprising first and second outerarms and an inner arm disposed generally between the first and secondouter arms, the first and second outer arms and the inner arm extendinglengthwise between the proximal body end and the distal body end; and anarray of electrodes configured to apply a neurostimulation therapywithin an epidural space of a patient, at least some of the electrodesbeing positioned along the first and second outer arms; wherein each ofthe first and second outer arms includes a resilient member that isbiased to flex the corresponding first and second outer arms from acollapsed condition to an expanded condition in a lateral direction awayfrom the inner arm, the resilient members permitting the correspondingfirst and second outer arms to flex toward the inner arm from theexpanded condition to the collapsed condition when a force is applied.2. The self-expanding lead of claim 1, wherein the inner arm includes asteering lumen at the distal body end, the steering lumen sized andshaped to receive an elongated tool for directing the lead body duringan insertion process.
 3. The self-expanding lead of claim 2, wherein thesteering lumen extends through the proximal body end to the distal bodyend.
 4. The self-expanding lead of claim 1, wherein the inner armincludes at least some of the electrodes from the array of electrodes.5. The self-expanding lead of claim 4, wherein the inner arm includes arespective resilient member that biases the inner arm to flex from acorresponding collapsed condition to a corresponding expanded condition,the resilient member of the inner arm permitting the inner arm to beflexed to the collapsed condition when the force is applied.
 6. Theself-expanding lead of claim 1, wherein the inner arm is a first innerarm and the lead body includes a second inner arm, each of the first andsecond inner arms including at least some of the electrodes of thearray.
 7. The self-expanding lead of claim 1, wherein the first andsecond outer arms partially define first and second elongated windows,respectively, the first and second elongated windows extending betweenthe proximal body end and distal body end and between the respectiveouter arm and the inner arm.
 8. The self-expanding lead of claim 7,further comprising a flexible membrane that is coupled to the lead bodyand covers at least one of the first and second elongated windows. 9.The self-expanding lead of claim 7, wherein the lead body has oppositepaddle sides when the first and second arms are in the expandedconditions, the self-expanding lead further comprising a flexiblemembrane that is coupled to the lead body and covers at least one of thepaddle sides.
 10. The self-expanding lead of claim 1, wherein each ofthe first and second arms has an arm cross-section that includes firstand second dimensions, the first and second dimensions beingperpendicular with respect to each other and differing by at most 50%.11. A self-expanding lead comprising: first and second outer armsextending between respective base and distal arm ends; an inner armdisposed generally between the first and second outer arms, the innerarm extending between a respective base end and a respective distal armend, the base ends of the inner arm and the first and second outer armsbeing coupled to each other proximate to a proximal body end of theself-expanding lead; and a multi-electrode array including a pluralityof electrodes, the first and second arms including at least oneelectrode of the multi-electrode array, wherein each of the first andsecond outer arms includes a resilient member that is biased to flex thecorresponding first and second outer arms from a collapsed condition toan expanded condition in a laterally-outward direction, the resilientmembers permitting the corresponding first and second outer arms to flexin a laterally-inward direction from the expanded condition to thecollapsed condition when a force is applied; wherein the electrodes ofthe multi-electrode array are configured to have predetermined positionswith respect to one another when the first and second outer arms are inthe expanded conditions in order to apply a neurostimulation therapywithin an epidural space of a patient.
 12. The self-expanding lead ofclaim 11, wherein the distal arm ends of the inner arm and the first andsecond outer arms are coupled to each other proximate to a distal bodyend of the self-expanding lead.
 13. The self-expanding lead of claim 11,wherein the inner arm includes a steering lumen, the steering lumensized and shaped to receive an elongated tool for directing the leadbody during an insertion process.
 14. The self-expanding lead of claim11, wherein the inner arm includes electrodes positioned along a lengthof the inner arm, the electrodes of the inner arm being part of themulti-electrode array.
 15. The self-expanding lead of claim 11, whereinthe inner arm is a first inner arm and the self-expandable lead alsoincludes a second inner arm, each of the first and second inner armsincluding electrodes that form part of the multi-electrode array. 16.The self-expanding lead of claim 15, wherein the first outer arm and thefirst inner arm are adjacent to each other and the second outer arm andthe second inner arm are adjacent to each other, the first outer arm andinner arm moving in a common direction toward the second outer arm andthe second inner arm when the lead is collapsed.
 17. The self-expandinglead of claim 11, wherein the self-expandable lead has opposite paddlesides when the first and second arms are in the expanded conditions, theself-expandable lead further comprising a flexible membrane that iscoupled to the lead body and covers at least one of the paddle sides.18. The self-expandable lead of claim 16, wherein the flexible membraneextends along only one of the paddle sides.
 19. The self-expanding leadof claim 16, wherein the flexible membrane has electrode openings thatexpose portions of the electrodes along the at least one paddle side.20. The self-expanding lead of claim 11, wherein each of the first andsecond arms has an arm cross-section that includes first and seconddimensions, the first and second dimensions being perpendicular withrespect to each other and differing by at most 50%.